Encountered the error message below while using our training labs? 

This error is generated when the IP address you used to start the lab has changed, breaking the lab whitelisting that gives you access.

Possible Causes:

1. Dynamic IP:
   Your IP may have changed due to a dynamic IP address assigned by your residential internet service provider (ISP). This can disrupt lab connectivity, especially if your IP changes mid-session.
2. SSL/TLS Interception:
   Traffic interception, commonly used in corporate networks for security monitoring, can interfere with secure WebSocket connections required for lab access.
3. Network Restrictions or Firewalls:
   Some networks — especially in corporate, school, or managed environments — may block the WebSocket (wss://) protocol or restrict traffic on required ports (such as 443 or 80), preventing labs from loading.
4. WebSocket Handshake Failure:
   If the browser cannot properly upgrade the connection from HTTPS to WSS (secure WebSocket), you may receive a connection error. This is often caused by misconfigured proxies or blocked protocols.
5. Unsupported Browsers or Cached Sessions:
   Older sessions or certain browser extensions may interfere with the lab client. Using incognito mode or switching browsers can often help.

6. Unstable Internet Connection:
   If your connection drops during lab initialization, the environment may fail to load or time out unexpectedly.

    

Troubleshooting Steps:

If you're seeing the error message when launching a lab, don’t worry - this can usually be resolved with a few quick checks. Here's what we recommend trying:

1. Start with a VPN (Most Reliable Fix):
   Connecting via a VPN has been the most effective workaround for clients experiencing this issue.

   • Choose a server near Europe or the UK for the best connection speed.

2. Check if Your IP is Changing:
   Some clients have dynamic IPs that change while loading the lab, which can disrupt the session.

   • You can use a tool like WhatIsMyIP to compare your IP before and after starting the lab.

   • If it changes, a VPN will help stabilize it.

3. Try Incognito or Private Mode:
   Opening the lab in a private browser window can avoid issues caused by old cached data.

4. Hard Refresh Your Browser:
   Perform a hard refresh (Ctrl + Shift + R or Cmd + Shift + R on Mac) to fully reload the lab page and clear any cached session issues.

5. Switch Browsers:
   Give both Chrome and Firefox a try — sometimes a different browser makes all the difference.

6. Terminate and Relaunch the Lab:
   If you’re stuck, fully close the lab session and relaunch it fresh. This can help re-establish the connection.

7. Test Another Lab:
   If other labs are working fine, the issue might be isolated to just one lab — and we’ll be happy to look into it.

8. Restart Your Router or Device (Optional):
   A quick reboot can help if your network has been running a while or you're on a dynamic connection.

Important Note for Corporate and VPN Users

If you’re accessing the labs from a corporate network, strict firewall policies, SSL inspection, or DNS filtering may block or interfere with the lab environment. Please ensure your IT department:

• Whitelists BTLO lab domains and services

• Allows WebSocket connections (wss://) over ports 443 and 80

• Disable SSL interception or inspection on our lab domains

You can request a full list of required domains from our support team if needed.

Still Not Working?

If the issue persists even after trying the above. Submit all of your findings to the support team. 

👉 Click here to open the support ticket form

• Take a screenshot of the full error message

• Open your browser’s developer console (F12 > Console tab) and capture any WebSocket or connection errors

• Details of What You Tried:
  Include info such as:

  • Lab name: (e.g., Linux System Hunt – BTL2)

  • Browser & version: (e.g., Chrome 114)

  • Network setup: (e.g., Home Wi-Fi with dynamic IP, VPN: ON/OFF)

  • Troubleshooting steps taken: (e.g., Used VPN, tried incognito, restarted lab 3 times, IP stayed the same)

We’ll review your report and follow up as quickly as possible.